Here's a place where I can post my thoughts on new papers, provide updates on my projects, and post info that will eventually be on my website The Theropod Database - http://theropoddatabase.com/ . It will center on theropods, but may delve into other topics as well such as phylogenetics.

Friday, December 2, 2011

Top 10 Most Poorly Described and Illustrated Mesozoic Theropods

Look at that, I managed to skip a month between posts. The hazards of coding, illness and other such excuses. Here's a quickie that was fueled by my annoyance at any significant primary literature while coding Adasaurus. These are the theropods whose publically available information is the most paltry compared to the completeness of their remains, and have been officially described already in the literature. The relative importance of the taxon isn't a factor, and taxa whose remains are lost aren't considered due to the impossibility of their redescription.

10. AnserimimusAnserimimus' holotype is a skeleton missing only some cervicals and the skull, but only the scapulocoracoid, manus and metatarsus were described and illustrated by Barsbold (1988). Kobayashi and Barsbold (2006) helped a bit, as does Bronowicz's (2011) fragmentary but well described specimens. But what keeps this from scoring higher is the availability of good photos of the mount (e.g. this) and Kobayashi's (2004) coding it for several matrices.

9. Tie between Cristatusaurus, Deltadromeus and Afrovenator
These taxa all have a common theme- Sereno described them (well, he described Suchomimus, which I sink into Cristatusaurus). Published by the king of the Science tabloid, featuring a Paulian skeletal and several zoomed in line drawings, these taxa have yet to be redescribed in detail. While there are photos of mounted skeletons available, these are all casts. The best source of information on these are the matrices of Rauhut (2003) and Benson (2010).

8. Aucasaurus
Basically complete, but only the proximal tail, arm and lower hindlimbs have been illustrated and briefly described. Recently, the braincase was also described, though I lack that paper so far. Ceratosaur matrices like Carrano and Sampson (2007) have some info.

6. "Chilantaisaurus" zheziangensis
Dong (1979) gave this proximal tibia and partial pes a fairly useless description and illustrated two pedal digits in ventrolateral view and curving towards the viewer. :| Therizinosaurian affinities have been suggested, but it's not been examined since.

5. Kaijiangosaurus
Only a few vertebrae, pectoral girdle and proximal/distal metatarsal outlines have been illustrated, and the description has yet to be translated from Chinese. An online photo shows a lot more is known, but also that size differences mean more than one individual/taxon are present.

4. Conchoraptor
Ah, Conchoraptor. You might be asking how can this be obscure when there are so many skeletons casted. I've even seen two in person. The problem with Conchoraptor is that it's unsure just which specimens belong to it, besides the holotype (of which we have illustrations of the skull, and a manus and metatarsus that presumably belong to it or a paratype). None of the articulated skeletons photographed online have the right manual proportions or slender metatarsal II, and crestless skulls like ZPAL MgD-I/95 (the one described by Osmolska, 1976 and which Kundrat has recently been describing braincase details of) and the one on Witmer's lab page identified as "Ingenia" could belong to other oviraptorids. No one has ever provided a modern diagnosis, described the holotype in any detail or justified the referral of other specimens. This makes depending on matrices more risky than for other taxa listed here, since their OTU could be chimaerical for all I know.

3. Rinchenia
This has been illustrated in the literature even more seldomly than Conchoraptor, since at least ZPAL MgD-I/95 has papers dedicated to it. We only have the skull, mandible, overly schematic ilium and a single caudal vertebra illustrated. Lucky for us, Auditore was able to obtain photos of the holotype and illustrate it as detailed by Cau on his blog. As for Conchoraptor, Norell et al. (2001), Lu (2004) and Maryanska et al. (2002) all provide codings, which can be trusted more for Rinchenia since there's only the holotype (though I note a recent incorrect trend of referring IGM 100/42 to it).

2. Adasaurus
The muse for this post only gets second place. For Adasaurus we must depend on a few schematic drawings (pelvis, metatarsus, pedal digit II), since Barsbold (1988) neither described it besides noting a couple features, nor does he allow photos to be circulated. There was a photo of the holotype online which has since disappeared, but shows Barsbold's pelvis illustration is inaccurate, and to make it worse Kubota (pers. comm. to Senter, 2010) indicates the supposed small sickle claw doesn't belong. I'm just hoping Kubota plans to redescribe the taxon like Kobayashi did for Barsbold's basal ornithomimosaurs. Until then, we depend on codings from Norell et al. (2001), Senter (2007) and Longrich and Currie (2009), and a few scattered notes. Hopefully Turner et al.'s upcoming dromaeosaurid monograph has some juicy photos.

1. Chilantaisaurus? sibiricus
There are a lot of fragmentary taxa known from a tooth or a vertebra that are poorly described (usually in a useless archaic way) and illustrated in a photo from a single view. What makes sibiricus stand out is that Riabinin (1914) didn't even identify which element the holotype was, let alone try to describe its features. He just said it was hollow and belonged to the limb of a fairly large theropod, probably a megalosaurid (named as Allosaurus? sibiricus). Even worse, he didn't illustrate it, only[Edit: Chure 2000 and Benson and Xu 2008 were incorrect about the lack of illustration and brevity of description; I've since examined the taxon here http://theropoddatabase.blogspot.com/2012/11/allosauruschilantaisaurus-sibiricus-is.html] providing six measurements (proximal width 48 mm, proximal depth 39 mm, distal width 68 mm, distal depth 62 mm, cavity width 22 mm, cavity depth 17 mm). Huene (1932) identified it as a distal metatarsal IV without rationale, but said only that it did not permit exact characterization and probably belonged to an allosaurid (renamed Antrodemus? sibiricus). Molnar et al. (1990) then said it was "almost identical with that of C. tashuikouensis in form and proportions of the distal condyle", so questionably referred it to that genus. You now possess the entirity of published information on sibiricus. Makes the available information on Adasaurus seem like an overflowing feast.

14 comments:

Would fail to mention Skorpiovenator, whose two size bars do not match, in the skull appears to be 27 cm in a 60 cm. The problem is that there are measures (nor in Ilokelesia for example, and the bars are quite dubious as to be taken seriously)

Another very bad is Bruhathkayosaurus although Theropoda is not whether to include as ex-Theropoda. Very poorly identified, poorly photographed and very badly drawn.

Teyuwasu and Dandakosaurus (do you really is a jaw?) Should be listed in my opinion.

Andrea, Can you give us the literature of the thesis Deltadromaeus please? I'll appreciate it and get it to quote, I recontruyendo to Bahariasaurus like a giant animal-like and Elaphrosaurus Limusaurus

Excellent news on Deltadromeus. While I think it's plausible that Bahariasaurus is a senior synonym (they don't have any published differences I find taxonomically valid), there's nothing published at present that allows me to combine them based on shared derived characters either. But maybe once Deltadromeus is described more completely...

Skorpiovenator is pretty briefly described, true. But at least we have a photo and reconstruction of the whole skeleton and skull.

Bruhathkayosaurus still wins as the dinosaur with the most poorly illustrated remains skill-wise, but I count it as a sauropod. And thanks for the offer, but I have the paper too.

Similarly, Teyuwasu may not be theropod, and should be illustrated by Huene (1942) anyway, though I haven't tracked down the volume with figures to that paper yet.

Dandakosaurus could certainly use redescription, but at least three of the five elements are illustrated, and all are described. I would like to know where Aravind got the idea there was cranial material known.

And yes, I received the Hou et al. 2002 data, though as can be seen by my last update being in March, I haven't had time to do much with it. But thanks!

I think, despite your use of Conchoraptor gracilis so readily, "Ingenia" yanshini is by far worse off, given the problems associated with referral of cranial material and being uncertain, just as much as with Concho, what displayed material is what, but with the added problem of the name. It is thus far more in need of revision and handling than any other oviraptorosaur, as it will help concretely define what specimens are likely to belong to other taxa formerly referred to it (including the Rinchenia issue where it is based on a specimen partially referred to "Ingenia"). Phew!

I guess you left Eoraptor lunensis out because there is a "planned" monograph, but there remains limited information on it as well.

At least with "Ingenia" we have most of the appendicular skeleton illustrated by Barsbold et al. (1990) and several good photos of the holotype publically available (Psihoyos, 1996; Nakasato website; despite its combination with other skulls). Though yes it desperately needs to be properly described.

Eoraptor would have been counted among the other Sereno taxa except that I have it as Saurischia incertae sedis, since it may be a sauropodomorph or basal eusaurischian.

Photos in art books (Psihoyos) and of mounts aren't description, especially if the mounts may be chimaeric. What is published of one (Barsbold, 1981, 1983; Barsbold et al., 1990, 2004) is published of the other (Barsbold, 1986; Barsbold et al., 1990, 2004). The latter two references for both are practically the same and are descriptive in the general for Oviraptoridae, not in the specific of the taxa in question, so they are described in essentially the same detail, with the exception that "Ingenia" received a treatment in the monograph (Barsbold, 1983) that Concho never did, but that is essentially a derivative of the 1981 treatment, so I'm not sure it counts (and it certainly doesn't treat the vertebrae and etc. that are so ridiculously under-treated for oviraptorids). Then, there's GIN 100/42.

I never said the available information had to be in technical literature. Note Anserimimus' information is in internet photos and a thesis for the most part. Various sources have confirmed that the "Ingenia" mount minus the head is indeed the holotype. Barsbold et al. (1990) is more useful for "Ingenia" than Conchoraptor, since it illustrates most of the appendicular skeleton of the former, but only the skull (already featured in Barsbold, 1976), manus (already featured in Barsbold, 1986) and metatarsus plus twon pedal unguals of the latter. The text is about equally useless for both, agreed. And true that IGM 100/42 doesn't have a detailed description or illustration yet, but it's not a named taxon so I didn't count it.

oviraptorids aRE BIRds so THEY ARE not dinosaURS OR THEROPOD ,\.AND HAVE SMOOD SKIN ON THERE BACK ALL DINOSAURS HAD THERMOREGULATION BUMPY SKIN ON THERE BACKS DINOSAURs is a kind of turtle a armo reptile

Congratulations idiotic anonymous commenter, your poorly written and inaccurate comment has finally led me to begrudgingly require logging in to comment here. I hope all of you who have written terribly constructed BAND comments and childish insults of Pickering are happy that you have slightly inconvenienced serious commenters. Hooray for jerks ruining privileges for everyone!

Rexisto, what I know about the thesis I mentioned is just a well supported rumor heard from a paleontologist friend of mine. Mickey, I agree with your comment on not combining Bahariasaurus and Deltadromeus until new evidence supports their synonymy.

Mickey, it doesn't matter whether or not Inosaurus is dinosaurian. The type and referred material of Inosaurus was found in three different horizons in North Africa, and there's a possibility that they may constitute separate taxa. Determining the systematic status of Inosaurus would require a redescription of all material described by Lapparent (1960) [except Spinostropheus, which has been redescribed by Sereno and colleagues]. For now, the best bet is to assign the Bahariya specimens to Therizinosauria indet. and restrict the name Inosaurus to the specimens from Niger.